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Gravity is real you dumb fuckers

And by that, I don't mean "will an apple fall if I let go of it" or "do the laws of gravitation as we know them really work?" I want to know if the messenger particle for gravity, the graviton, has been irrefutably proven to exist through observation, not just inference.

My understanding (I am not professional, nor even remotely on the cutting edge of physics - I just pay attention to concepts and like thinking about them) has been that gravitons were assumed to exist, down to having a certain mass and spin and whatever, but have never been detected. The explanation I heard was that they might be so tiny and near-massless that they don't exist in our universe for very long, and disappear instantly after doing their job here.

That's all well and good, and I certainly accept that as probably true, but it's not irrefutable in that just because something SHOULD be there based on what we've found out about physics, that doesn't mean it definitely is. And it does seem a bit weak to assume something exists, to the point of mocking alternative theories, and explain away the lack of direct proof just by saying "well, it fits the model so conveniently well, and we can't find them because... um... they're `unfindable!' Yeah, that's the ticket!" Indirect evidence is all well and good, and it's how we know tons of stuff about the universe, but I don't think it quite qualifies as "irrefutable." Otherwise, I could claim that tiny undetectable elves with pointy hats move objects toward each other and sit back and smugly cross my arms.

While there are lots of seemingly kooky "alternate theories" that degenerate into equally unproveable pseudo-science, it doesn't seem prudent to dismiss the possibility. I recall reading Everett's Many Worlds paper and thinking that some implications of that could eliminate the need for gravitons to exist to remain consistent with observations, even though the existence of gravitons is assumed in the paper anyway. I often think that what appears to be "gravity" could just be a consequence of massive objects "denting" spacetime and allowing that all objects move along that curvature, which is "steeper" near more massive bodies - it seems to me that that would allow for behavior consistent with the math behind gravity but preclude the need for an actual particle to be part of the mechanism.

Some science teacher at my school said that this was wrong, and that gravitons HAVE been reliably and irrefutable observed. Is this true? Where, when, and how was this done? If so, was I completely and utterly mislead or is it recent enough that my impression WAS valid in the past, but has since been rendered moot?

I'm trying to recall other "alternative" theories that still fit the math, however seemingly fanciful - like the one that had all matter "growing" at a constant rate. Just as unverifiable as "unobservable mystery particles that fit conveniently," but assuming I wasn't completely misinformed, certainly not dismissable in favor of something else based on that criteria alone.

I'll save wondering if time and motion are also illusions for another time...

EDIT: Why did some dumb fucker change the title of this thread, especially considering how obvious it is from the discussion in this thread that the original was a much more valid title? :rolleyes:

Gravity is only "true" in the sense that it seems to behave the way some scientists have predicted it to. But no one can disprove the fact that God actually makes things fall. Like, personally makes them fall with his hand. Basically, it's just a theory.

I hope playing the Joker didn't have anything to do with this... I mean, I hope he wasn't driven to kill himself because of the role in some way. He was clearly taking the part pretty goddamned seriously.

only a quantum theory of gravity relies on gravitons. Who's to say that theory is right?

edit: if this blows your mind, try learning some solid state physics. A course in that will basically be learning 20 different models, each only applicable in certain situations because none of them are actually what occurs.

edit: if this blows your mind, try learning some solid state physics. A course in that will basically be learning 20 different models, each only applicable in certain situations because none of them are actually what occurs.

Technically speaking the models you learn are actually just approximations which give analytical results because you are dealing with literally a huge number of entities which is just impossible to do precisely.

If I was kidnapped, woke up in a lab, told they were going to replace my vocal cords with those of Tony Jay, and lock me in a sound booth until the day I die I would look those bastards right in the eye and say "Alright you sons of bitches lets do this. This one is for the children."

When I jump out of a plane, I want a parachute. Therefore, gravity is real enough to me. Observation notes that this is a pretty universal phenomenon. Find me some people who regularly jump out of (flying) planes without parachutes, then we can talk.

As for gravitons, I'll leave that up to the physicists.

[I may be getting this wrong & ELC or someone correct me if so, but if you want mystery theories etc, some principles of quantum physics are pretty good, especially the one that updates the old "observing a thing can change a thing" idea to "observing a thing can [i]create[/i] a thing" which is an interesting existential mindfuck]

like the one that had all matter "growing" at a constant rate. Just as unverifiable as "unobservable mystery particles that fit conveniently,"

Isn't that just one of the Big Bang expanding universe theories? I misunderstood that for the longest time, assuming expanding universe = stuff being created at the edge, but apparently it simply means that everything, everywhere, is slowly getting bigger.

Does a black hole have mass or is it the stuff that was collected that gives it mass and a stronger gravitational pull?

I'd also wonder if there's a limit to how much you can compact matter - if I took all the matter in the Milky Way and compacted it to the size of a pebble, how would gravitons work if all matter is present in one tiny space? Would the 'pebble', despite being dense, have no gravitational pull?

Does a black hole have mass or is it the stuff that was collected that gives it mass and a stronger gravitational pull?

I'd also wonder if there's a limit to how much you can compact matter - if I took all the matter in the Milky Way and compacted it to the size of a pebble, how would gravitons work if all matter is present in one tiny space? Would the 'pebble', despite being dense, have no gravitational pull?

All matter in the universe compacted to a pebble would be a pre-big bang state. The laws of physics as we understand them simply don't apply to conditions prior to the big bang.

Does a black hole have mass or is it the stuff that was collected that gives it mass and a stronger gravitational pull?

I'd also wonder if there's a limit to how much you can compact matter - if I took all the matter in the Milky Way and compacted it to the size of a pebble, how would gravitons work if all matter is present in one tiny space? Would the 'pebble', despite being dense, have no gravitational pull?

All matter in the universe compacted to a pebble would be a pre-big bang state. The laws of physics as we understand them simply don't apply to conditions prior to the big bang.

Does a black hole have mass or is it the stuff that was collected that gives it mass and a stronger gravitational pull?

I'd also wonder if there's a limit to how much you can compact matter - if I took all the matter in the Milky Way and compacted it to the size of a pebble, how would gravitons work if all matter is present in one tiny space? Would the 'pebble', despite being dense, have no gravitational pull?

All matter in the universe compacted to a pebble would be a pre-big bang state. The laws of physics as we understand them simply don't apply to conditions prior to the big bang.

How about just the matter in a galaxy?

That would be sort of like a singularity (black hole), except that the size of a singularity cannot be measured in inches and such, but can be measured in mass. And yes, it would indeed have an enormous mass, and would exert a gravitational pull proportional to that mass.

And by that, I don't mean "will an apple fall if I let go of it" or "do the laws of gravitation as we know them really work?" I want to know if the messenger particle for gravity, the graviton, has been irrefutably proven to exist through observation, not just inference.

My understanding (I am not professional, nor even remotely on the cutting edge of physics - I just pay attention to concepts and like thinking about them) has been that gravitons were assumed to exist, down to having a certain mass and spin and whatever, but have never been detected. The explanation I heard was that they might be so tiny and near-massless that they don't exist in our universe for very long, and disappear instantly after doing their job here.

This is potentially true, but there's insufficient evidence to draw any firm conclusions. We're working on a best guess until we've a reliable means of observing any gravity boson.

Check out some of the articles here for more information on what I'd consider to be the current best run facility operating in that direction.

We know oxygen is real because we've determined several things about how it works, what it does, and what it's made of.

However, before the 1800s (iirc) you could just as easily have said that oxygen didn't exist at all, because nobody had defined it. The natural philosophers had phlogisten theory. In addition to the four Aristotelian elements (fire, earth, air, and water) they added phlogisten, a fifth element that (like oxygen) is responsible for combustion.

Was phlogisten real? It was a definition that usefully explained a phenomenon. It's now obselete, but only because it has been replaced with the idea of "oxygen," in the same way that Newtonian gravity is obselete and has been replaced with relativity-gravity.

Ultimately, "oxygen" and "gravity" are just words that are fitted with definitions, and those definitions are fitted with theories about observable reality that are inevitably going to be incomplete. This doesn't mean the phenomena the words are attempting to signify doesn't exist.

We know oxygen is real because we've determined several things about how it works, what it does, and what it's made of.

However, before the 1800s (iirc) you could just as easily have said that oxygen didn't exist at all, because nobody had defined it. The natural philosophers had phlogisten theory. In addition to the four Aristotelian elements (fire, earth, air, and water) they added phlogisten, a fifth element that (like oxygen) is responsible for combustion.

Was phlogisten real? It was a definition that usefully explained a phenomenon. It's now obselete, but only because it has been replaced with the idea of "oxygen," in the same way that Newtonian gravity is obselete and has been replaced with relativity-gravity.

Ultimately, "oxygen" and "gravity" are just words that are fitted with definitions, and those definitions are fitted with theories about observable reality that are inevitably going to be incomplete. This doesn't mean the phenomena the words are attempting to signify doesn't exist.

Newtonian gravity is obsolete the same way supercomputers have made pocket calculators obsolete.

Does a black hole have mass or is it the stuff that was collected that gives it mass and a stronger gravitational pull?

I'd also wonder if there's a limit to how much you can compact matter - if I took all the matter in the Milky Way and compacted it to the size of a pebble, how would gravitons work if all matter is present in one tiny space? Would the 'pebble', despite being dense, have no gravitational pull?

err... black holes are collapsed stars several times larger than Sol.

they have mass to start with.

depending on your concept of how a black hole works, and if it is a naked singularity or not, it may or may not gain mass as it eats stuff.

Gravatons have not been shown to exist. Nor has any mechanism for gravity. There are several diffrent ideas for how it happens, and theories that allow us to predict gravity's force, but we don't really know how it happens.

When I can smell colours, it's how I know that my mescaline is quality.

Does a black hole have mass or is it the stuff that was collected that gives it mass and a stronger gravitational pull?

I'd also wonder if there's a limit to how much you can compact matter - if I took all the matter in the Milky Way and compacted it to the size of a pebble, how would gravitons work if all matter is present in one tiny space? Would the 'pebble', despite being dense, have no gravitational pull?

All matter in the universe compacted to a pebble would be a pre-big bang state. The laws of physics as we understand them simply don't apply to conditions prior to the big bang.

Actually, big bang state would be all matter in the universe compacted into a zero-dimensional manifold, i.e. a point. Space and time did not exist until after the big bang. Also, keep in mind that terms like "prior" and "pre" don't really work when talking about the big bang, considering time didn't exist until after the big bang occurred and cause-effect relationships didn't either.

Does a black hole have mass or is it the stuff that was collected that gives it mass and a stronger gravitational pull?

I'd also wonder if there's a limit to how much you can compact matter - if I took all the matter in the Milky Way and compacted it to the size of a pebble, how would gravitons work if all matter is present in one tiny space? Would the 'pebble', despite being dense, have no gravitational pull?

All matter in the universe compacted to a pebble would be a pre-big bang state. The laws of physics as we understand them simply don't apply to conditions prior to the big bang.

Actually, big bang state would be all matter in the universe compacted into a zero-dimensional manifold, i.e. a point. Space and time did not exist until after the big bang. Also, keep in mind that terms like "prior" and "pre" don't really work when talking about the big bang, considering time didn't exist until after the big bang occurred and cause-effect relationships didn't either.

...

From a totally unscientific viewpoint, has nobody in the scientific community pointed out that the Big Bang is an extraordinarily silly theory? Isn't, "we don't have a fucking clue" good enough?

Does a black hole have mass or is it the stuff that was collected that gives it mass and a stronger gravitational pull?

I'd also wonder if there's a limit to how much you can compact matter - if I took all the matter in the Milky Way and compacted it to the size of a pebble, how would gravitons work if all matter is present in one tiny space? Would the 'pebble', despite being dense, have no gravitational pull?

All matter in the universe compacted to a pebble would be a pre-big bang state. The laws of physics as we understand them simply don't apply to conditions prior to the big bang.

Actually, big bang state would be all matter in the universe compacted into a zero-dimensional manifold, i.e. a point. Space and time did not exist until after the big bang. Also, keep in mind that terms like "prior" and "pre" don't really work when talking about the big bang, considering time didn't exist until after the big bang occurred and cause-effect relationships didn't either.

...

From a totally unscientific viewpoint, has nobody in the scientific community pointed out that the Big Bang is an extraordinarily silly theory? Isn't, "we don't have a fucking clue" good enough?

uhh... it's like this. We know the universe has been expanding for as long as we can measure it(a long time, thanks to the whole thing of light taking time to get places). All the math indicates that everything was very close together and rapidly expanded from something very close to a single point, ever so slightly after the universe formed.

Unless you are a YEC, there isn't too much to debate there.

All big bang theory says is that just before math starts working, everything was a single point when the universe started. It's not really that silly, it just is the best summery of the information that we have.

All big bang theory says is that just before math starts working, everything was a single point when the universe started. It's not really that silly, it just is the best summery of the information that we have.

Surely "not enough information to suggest a conclusion" is the best summary of the information that we have?

I'll take Incenjuar's answer, especially since the books I read were most likely even more out of date. Or more to the point, the same books, but very up to date.

"Time, Space et c are all constant rules of physics, except for before this point here, where they weren't, and possibly after this point here, where they won't be again"

As I've understood it, Big Bang theory is about as consistent with all other theories of physics etc as Intelligent Design is with evolution. I might be misunderstanding it, but I haven't seen a satisfactory explanation for the pre-existence of this material which supposedly was released with the Big Bang, which fits any of the current constant laws of science. Which either suggests the constant laws are wrong, or Big Bang theory is, and my money is on the latter.

Not Sarastro: Basically, no. Why would you expect that the laws of physics would be constant everywhere in spacetime? I say spacetime deliberately, because not only do people spend a lot of time worrying about whether or not the laws change in other places (the technical term is local gauge invariance in the way it is usually discussed). On the other hand, the experimental evidence for a Big Bang is pretty fucking solid.

As to gravity- gravity is real. Gravity waves are predicted by GR (which is well verified) and energy loss due to gravity waves has been observed (in the two-pulsars orbiting each other experiment, if need be I can look up the paper and cite it to you). Gravitons may not be real. Our understanding of quantum gravity doesn't rely entirely on one theory- nobody will commit suicide if we find out that there is no such thing as a graviton.

Matter can't go where energy is absent, right? Absolute zero and all that - so is dark energy only outside the fringes of space? But if you did have matter suspended in space where there is no energy, there'd be no gravity, lykouragh?

Does a black hole have mass or is it the stuff that was collected that gives it mass and a stronger gravitational pull?

I'd also wonder if there's a limit to how much you can compact matter - if I took all the matter in the Milky Way and compacted it to the size of a pebble, how would gravitons work if all matter is present in one tiny space? Would the 'pebble', despite being dense, have no gravitational pull?

All matter in the universe compacted to a pebble would be a pre-big bang state. The laws of physics as we understand them simply don't apply to conditions prior to the big bang.

Actually, big bang state would be all matter in the universe compacted into a zero-dimensional manifold, i.e. a point. Space and time did not exist until after the big bang. Also, keep in mind that terms like "prior" and "pre" don't really work when talking about the big bang, considering time didn't exist until after the big bang occurred and cause-effect relationships didn't either.

...

From a totally unscientific viewpoint, has nobody in the scientific community pointed out that the Big Bang is an extraordinarily silly theory? Isn't, "we don't have a fucking clue" good enough?

Trying to discuss "silly" as relates to science is silly. "Silly" is a subjective concept that deals only with one's knowledge and, by extension, their expectations. It has nothing to do with reality.

Because in day to day life we expect there to be limits to how much matter can be compressed into any given space, which is both meaningless when talking about the big bang but also irrelevant when talking about cosmological scales.

@Armageddon, my problem is more with the pre-Big Bang state, not the concept of the universe expanding per se.

@Drez, since I explicitly said that my observation was totally unscientific, your pedantry is pretty obsolete.

@Lykouragh: If the laws of physics don't remain constant then it isn't really a problem, but I notice that you weren't exactly jumping on board with that idea, more saying that people question whether they do remain constant. I imagine the idea that they don't remain constant must throw up quite a lot of problems with previous theories? I know this happens a lot (updating relativity, Newtonian physics vs Quantum physics etc), but doesn't it somewhat undermine current / just previous theories of how things work?

On the other hand, experimental evidence for the Big Bang? Tell me more.

@Drez, since I explicitly said that my observation was totally unscientific, your pedantry is pretty obsolete.

Apparently my use of the word "science" in the post you are referring to led you to believe I was criticizing you in that fashion, so let me state - emphatically - that I think your unscientific "observation" is nonsense as well. Silliness is a nonsensical concept in every context given the subject at hand. I mean, were you really asking "do all of you look up at the heavens and chuckle?" Because that is, more or less, what you seem to be asking.

If you're asking "is it silly" in the sense of "is this theory silly" then I'd suggest there is nothing "unscientific" about the observation anyway. The theory is a part of science and you are saying that you find the concept silly regardless of whatever may be real. I mean, I don't know how to respond to this except as I did above: "silliness" is silly, here.

I'd say my pedantry is on the mark. Don't be silly.

Drez on December 2007

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Apothe0sisHave you ever questioned the nature of your reality?Registered Userregular

As I've understood it, Big Bang theory is about as consistent with all other theories of physics etc as Intelligent Design is with evolution. I might be misunderstanding it, but I haven't seen a satisfactory explanation for the pre-existence of this material which supposedly was released with the Big Bang, which fits any of the current constant laws of science. Which either suggests the constant laws are wrong, or Big Bang theory is, and my money is on the latter.

You haven't understood it.

The big bang in no way involves the explosion of matter into space. It isn't that there was a single dense point of matter within spacetime which exploded, it's a whole 'nother kettle of eels.

The big bang (in its most naive presentation, because I'm not a physicist) runs like this.

At t=0, the UNIVERSE is infinitely curved (i.e. spacetime is a point)
As t -> now we see a number of stages

First of all inflation, the unfolding of space, very quickly. During this period the universe remains very hot and dense with energy. There is no matter in the universe only energy which is very dense because the amount of energy within the universe remains the same as it is today, but the universe is but a tiny fraction of the size.

Next coalescence, the universe continues to expand, which effectively cools the universe a little. It becomes cool enough for Strong Atomic Force (IIRC) to overcome the latent temperature while also being hot enough for matter to coalesce.

The universe cools further and the quarks which coalesced are now cool enough to combine and form protons and neutrons and electrons. Which, as the universe continues to expand and thus cool, can combine to form ions and then atoms when they are cooler still.

Now, gravity starts to come into play, the universe continues to expand and the relatively weak force of gravity is enough to form little whorls and eddies in the cosmic soup of bits of stuff. Slowly matter accretes, which increases the force of gravity in that area, which allows it to suck in more matter, which continues the feedback loop. Eventually, we end up with supermassive stars, which have relatively short lifespans, which then go supernova and the whole accretion thing starts again which exciting new elements and smaller stars (which ultimately leads to solar systems like our own).

First of all, it makes no sense to ask where the matter came from that was involved in the big bang, because A) there wasn't any, and B) it came from coalescence, pay attention next time. Now, there is also no point in asking where the energy came from that suffused the universe right from t=0 because there was never a time that it did not exist. Asking about "before the big bang" makes little sense because the passge of time starts when the big bang happens, questions about "well where did the singularity come from then?", are not self-evidently coherent.

There are better more complicated big bang theories which involve colliding 6D-branes and all sorts of other madness. They do not however make the question of "well where did the energy come from?" any more sensible, as ultimately, something somewhere begins with energy in it as part of the theories. The so-called "common-sense" intuition that it has to ultimately have some sort of origin is spurious, it appears to be the case that the energy has always existed in some form from go to woah. Even where that not to case, ideas of the impossibility something from nothing, or rules internal to the universe applying to the universe itself or "outside the universe" (as much as that may or may not make sense) are spurious. If something is truly "nothing" then there can be no rules which apply to it. On the other hand, there is no reason to believe that the conservation of matter/energy applys externally to the universe. Plus, as t-> 0 the various equations we use to describe the behaviour of the universe stop giving sensible answers (i.e. physics breaks down).

TL;DR - There is a very good answer as to the origins of matter - Coalescence. The big bang is the explosion of the universe itself, not of matter. So called common sense is stupid and you're stupid if you think that you can defeat the big bang with it.

Apothe0sis on December 2007

Tide goes in. Tide goes out.
Es-annon NEVA 4GET

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Apothe0sisHave you ever questioned the nature of your reality?Registered Userregular

He was harping on about 'silly' being an unscientific term, when I had said I wasn't speaking scientifically. It's also fairly obvious that 'silly' is a descriptive term, not a quantitative one, so picking on it is pretty, well, silly.

Thanks for your explanation, the bit which I'm questioning isn't actually the existence of matter (my bad terminology previously), but the first mover question of energy that you addressed at the end. In fact, my point wouldn't even be the existence of that energy, but (I suppose) the motion of it. Whatever prompted the energy to change from the form of: no universe, to: universe. This doesn't necessarily require time concepts of before, after, etc within spacetime, and I understand (though don't totally accept) the principle that there is no 'before' if the Big Bang creates time. It also doesn't require notions of 'nothing to something'. But if, as you say, these theories all start with energy inherent in a process somewhere, it is causing change as part of that process, and has been involved in all the changes of state since. Did previously it just...not?

It seems to me like something of an infinity paradox - however you describe it, in whatever terms, you are still talking about an effect, and thus presumably a cause. Or not - perhaps just random effects? In which case, is there any particular reason people think that the universe will not simply stop existing just as it started?

I can only equate it with what seems to me to be a basic flaw with the mathematical principle of infinity (real infinity, not the theoretical use, or approximations where something is so big it is assumed to be infinite), namely that the whole process of mathematics up until that point is quantitative - a thing is one more than the previous thing - until this point where it is suddenly infinite; a completely unquantifiable concept. It seems to disprove either itself or all of the mathematics before it.

Or (actually) an old 19th/20th century model of atoms, before they had discovered the latest subatomic particles, where first the atom, then the electron, proton, neutron, then quarks (etc etc) were the smallest possible particle. There was a tendency among many scientists to say, instead of: we don't know what is smaller, or we haven't discovered what is smaller, that simply there was nothing smaller. This pretty obviously went against all the evidence that each thing was a composite of smaller things (nucleus -> atom -> molecule -> compound and so on), and the theoretical systems that we had devised to explain this - and lo and behold, we discovered quarks and such. I'm wondering whether the energy for the Big Bang, & the concept of actual infinity, aren't just similar failures in our ability to say: we don't know yet?

Whatever prompted the energy to change from the form of: no universe, to: universe.

There was no prompting. In order for there to be a prompt, there would have to be time prior to its initial state. The initial state needs no prompt because it is always already tending towards expansion. By its very nature in that state it must expand.